Frost line depth in DeKalb County, MO
How deep the ground freezes in DeKalb County, MO
31 in. Dig to 31 in, just below the frost. Nearest NOAA station: Amity 4 Ne, 2.5 mi.
Your building department sets the legal frost line depth (IRC Table R301.2(1)); footings must go below it (R403.1.4.1). Call them before you dig.